Be open to change. Recognize that no matter how much you prep, there is always a chance that your players will go the complete opposite direction, and that is OKAY. The ability to improvise, adjust and adapt will serve you well.

Most "advice" people give is just preferential, imo. But, there are a few tidbits I think are universal to a good game:

Above all, do not have a course of action in mind for your players. The best part of an RPG is the go anywhere, do anything aspect. If you stifle that, it will not be fun. I promise you. Let them go anywhere, do anything. Play to find out what happens, not to guide them through your plot. This is why I prefer scenario-based adventures instead of path-based adventures. But, you can do it with both.

Be a fair arbiter of the rules. When in doubt, judge on the side of your players. With that said, do not feel beholden to the rules. If something doesn't make sense, change it. Confer with your players as to what they think.

Your players will look to you to settle disputes, guide the group, and set the tone. Lead by example and be passionate about your game. Don't feel like all the burden should be on you to make the game fun. Having good players is just as important as a good DM.

Playing an RPG is sort of like playing in a band; it's most fun before it gets too serious and works best when everyone is riffing off each other's contributions. Don't take things too serious and make sure everyone's contributions are appreciated. Also, like playing in a band, you'll probably suck at first and make mistakes. Don't worry. You'll get better.

Like both of the above, you can plan, but the true enjoyment in DMing is watching how your players react to a situation that you provide, be open and able to think of things on the fly, because you will need it. I would suggest looking at a premade module if you are planning on running an ongoing campaign to start, and try watching some videos around it, like if you run Curse of Strahd watch Chris Perkins DM it, and see how he differentiates the story to fit his players, this is just to give you a good basis to how to deal with players going their own path, because they will do that. Tailor to your skills, each GM has their own thing that they are exceptionally good at, Mike above is very good at creating a picture in your head, so he makes sure that is on full display any game he runs, Justin is good at seeing 100 different ways for doing something but still being adaptable when a player wants to do something different, I am good at building a player into a campaign and engaging them in a larger quest with their own personal buy in. Most of all have fun, if you do not enjoy DMing, then your players probably wont enjoy the game, and it is okay to not enjoy dming, it is not for everyone.